Conventionally, proposals have been made for a composite material having desired electrical conductivity by blending a carbon material such as carbon black into a resin. In recent years, along with the advancement of device performance, there have been demands for further enhancement of the functionality of materials. In view of the circumstances, attempts have been made to blend, as a material having excellent electrical conductivity and contributing to excellent machine characteristics, a carbon nanotube instead of conventional carbon materials.
It is known that vulcanizing a composition, which is obtained by blending a cross-linker and a carbon nanotube with a hydrogenated carboxylated nitrile rubber having heat resistance, ozone resistance, chemical resistance, and oil resistance, allows an increase in tension strength and elasticity modulus of the nitrile rubber while maintaining elongation at breakage and distortion characteristics (see Patent Literature 1).
In addition, Patent Literature 1 discloses, as a rubber material for tires, an elastomer composition in which 0.1 to 150 parts by weight of carbon nanotube is blended with 100 parts by weight of an elastomer. The elastomer composition is obtained by mixing carbon nanotube slurry with an elastomer solution or with latex, and then coagulating the mixture. Patent Literature 1 teaches that the carbon nanotube slurry is obtained by (i) mixing a carbon nanotube with water or a solvent in combination with an emulsifier and/or a dispersant as needed and then (ii) homogenizing the mixture with the use of a stirrer. Patent Literature 2 notes that a short carbon nanotube having a length of 100 nm or less is preferable in light of its dispersibility.
Patent Literature 3 discloses a formed product obtained by (i) dispersing a single-walled carbon nanotube into water in the presence of gum arabic or SDS, thereby obtaining a dispersion liquid, (ii) mixing the dispersion liquid with polystyrene-based latex or polyethylene-based latex, thereby obtaining a mixture, (iii) freeze-drying the mixture so as to obtain a composition, and then (iv) heat forming the composition.
Meanwhile, a proposal has recently been made for a method that significantly increases activity and lifetime of a catalyst by, in employing the CVD method, causing a catalyst activation material such as water, along with material gas, to come into contact with the catalyst (this method will be hereinafter referred to as “super-growth method”; see Non-Patent Literature 1).